Re: [Haskell-cafe] GHC Api typechecking

Looking at the code for GHC, it turns out that your use case is not supported. It is not allowed to have in-memory-only files. If you specify a buffer it will still try to find the module file on the disk, but it will (or at least should) use the contents from the specified string buffer. I've been thinking about changing the Finder (the part that maps module names to source files and .hi files) to use a notion of a virtual file. This way, the API client could define how and where data is stored. On 18 April 2010 11:01, Phyx wrote:

Hi,

I checked out how Hint is doing it, but unfortunately they're calling a function in the GHC api's interactive part to typecheck a single statement, much like :t in ghci, So I can't use it to typecheck whole modules. I've tried working around not being able to construct a TargetId but ran into another wall. I can't find anyway to do dependency analysis on the in-memory target, so the dependency graph would be empty which is ofcourse a big problem.

Does anyone know if Leksah uses the GHC api for typechecking? And if it only gives type errors after you save a file?

The code I've been trying is

typeCheckStringOnly :: String -> IO (ApiResults Bool) typeCheckStringOnly contents = handleSourceError processErrors $  runGhc (Just libdir) $ do    buffer <- liftIO $ stringToStringBuffer contents    clock  <- liftIO getClockTime    dflags <- getSessionDynFlags    setSessionDynFlags dflags    let srcLoc   = mkSrcLoc (mkFastString "internal:string") 1 1        dynFlag  = defaultDynFlags        state    = mkPState buffer srcLoc dynFlag        parsed   = unP Parser.parseModule state        pkgId    = stringToPackageId "internal"        name     = mkModuleName "Unknown"        mod'     = mkModule pkgId name        location = ModLocation Nothing "" ""        summary  = ModSummary mod' HsSrcFile location clock Nothing [] [] "" dynFlag Nothing    (\a->setSession $ a { hsc_mod_graph = [summary] }) =<< getSession    case parsed of       PFailed _ _        -> return $ ApiOk False       POk newstate mdata -> do let module' = ParsedModule summary mdata                                check <- typecheckModule module'                                return $ ApiOk True

this fails with a ghc panic

: panic! (the 'impossible' happened)  (GHC version 6.12.1 for i386-unknown-mingw32):        no package state yet: call GHC.setSessionDynFlags

Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

:(

Cheers, Phyx

-----Original Message----- From: Gwern Branwen [mailto:gwern0@gmail.com] Sent: Saturday, April 17, 2010 20:59 To: Phyx Subject: Re: [Haskell-cafe] GHC Api typechecking

On Sat, Apr 17, 2010 at 1:49 PM, Phyx wrote:

...

Hi all, I was wondering if someone knows how to do the following:

I’m looking to typecheck a string using the GHC Api, where I run into problems is that I need to construct a Target, but the TargetId only seem to reference physical files.

Ofcourse I can write the string to a file and typecheck that file, but I would like to do it all in memory and avoid IO if possible.

Does anyone know if this is possible?

For the record I’m trying to create the target as follows

createTarget :: String -> IO Target

createTarget content =

 do clock  <- getClockTime

    buffer <- stringToStringBuffer content

    return $ Target { targetId           = TargetModule (mkModuleName "string:internal") ß problem

                    , targetAllowObjCode = True

                    , targetContents     = Just (buffer,clock)

                    }

typeCheckStringOnly :: String -> IO (ApiResults Bool)

typeCheckStringOnly contents = handleSourceError processErrors $

runGhc (Just libdir) $ do

    dflags <- getSessionDynFlags

    setSessionDynFlags dflags

    target <- liftIO $ createTarget contents

    addTarget target

    load LoadAllTargets

    let modName = mkModuleName "string:internal" ß problem again, don’t know how to create the dependency graph then.

    graph <- depanal [modName] True

    (\a->setSession $ a { hsc_mod_graph = graph }) =<< getSession

    value <- fmap typecheckedSource (typeCheck modName)

    return $ ApiOk True

Cheers,

Phyx

Have you looked at how the Hint package does things?

-- gwern

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